Retroreflective materials are employed for various safety and decorative purposes. A demand exists for retroreflective materials having discernible patterns, graphics or validation images formed thereon. The discernible patterns or graphics may be directional or non-directional. A directional image produces a varying appearance at different angles of view.
A validation image, such as a watermark, is an identifying pattern or legend either on or in a material to provide validation of the material. Retroreflective sheeting with directional and non-directional watermarks have been used as a validation means for documents, cassette tapes, compact disk containers, digital versatile disk (DVD) containers, electronic devices, traffic signage and license plates.
One problem with watermarks on retroreflective material is providing the watermark in a manner that provides the needed authentication but that provides some subtlety or inconspicuousness, such as being discernible in relatively few angles of viewing. Often expensive processing steps and equipment are required to provide such a watermark. Additionally, there is generally little processing control over the conspicuousness or intensity of the watermark.
It is desirable to have an image that is distinct and viewable for authenticating purposes. Further, it is desirable to have a high speed, high quality, low cost process of producing discernible patterns for graphic, decorative and other utilitarian purposes on retroreflective sheeting.